Inoculation Improves Microbial Manganese Removal during the Start-Up of Rapid Sand Filters

Area of Science:

• Environmental Science
• Microbiology
• Water Treatment Engineering

Background:

• Long start-up times for manganese removal in rapid sand filters present challenges for drinking water treatment.
• Groundwater often contains iron, ammonium, and manganese, requiring effective removal processes.

Purpose of the Study:

• To assess the start-up dynamics of manganese removal in dual-media rapid sand filters.
• To evaluate the impact of inoculating filters with biologically active sand on removal efficiencies.

Main Methods:

• Two full-scale dual-media rapid sand filters were inoculated with 20% biologically active coated sand.
• Monitoring of ammonium and manganese removal efficiencies, manganese oxide formation, and microbial community changes (16S rRNA, qPCR).
• X-ray spectroscopy was used to analyze manganese oxide structures.

Main Results:

• Inoculation achieved initial ammonium and manganese removal efficiencies of 60-70% and 30-50%, respectively.
• Complete ammonium removal took ~8 weeks, while manganese removal required 17-25 weeks.
• Full manganese removal correlated with 50% ammonium removal in the anthracite layer, and manganese oxides resembled δ-MnO2.

Conclusions:

• Inoculation with biologically active filter medium significantly enhances ammonium and manganese removal during filter start-up.
• Microbial manganese oxidation, potentially involving Nitrospira, plays a key role in manganese removal.
• This inoculation strategy offers a promising method to improve rapid sand filter performance and reduce start-up times.